Inhaled Corticosteroids and the Lung Microbiome in COPD

Advancements and challenges in the management of pneumonia in elderly patients with COPD

INTRODUCTION

Chronic Obstructive Pulmonary Disease (COPD) significantly predisposes the elderly to pneumonia, presenting a complex interplay of pulmonary dysfunction and infection risk.

AREAS COVERED

This article reviews the substantial epidemiologic impact, elucidates the interlinked pathophysiology of COPD and pneumonia, and examines the microbial landscape shaping infection in these patients. It also evaluates management protocols and the multifaceted clinical challenges encountered during treatment.

EXPERT OPINION

Delving into the latest research, we underscore the criticality of preventive measures such as vaccination and present an integrated approach to managing Community-Acquired Pneumonia (CAP) in the COPD demographic. The review also proposes strategic directions for future investigations aimed at enhancing patient outcomes through a deeper understanding of the COPD-pneumonia nexus.

Inhaled Corticosteroids and the Risk of Nontuberculous Mycobacterial Infection in Chronic Airway Disease: A Nationwide Population-Based Study

BACKGROUND

Chronic airway diseases, such as asthma and chronic obstructive pulmonary disease (COPD), are increasingly being treated with inhaled corticosteroid (ICS). However, ICSs carry potential infection risks, particularly nontuberculous mycobacteria (NTM). This study investigated the association between ICS use and NTM infection risk using national insurance data, particularly for individuals with chronic airway diseases.

METHODS

We conducted a nationwide population-based study using data from the National Health Insurance Service-National Sample Cohort in South Korea from 2002 to 2019. The cohort included 57,553 patients diagnosed with COPD or asthma. To assess the risk of NTM infection, we used Cox proportional hazards models and propensity score-based inverse probability of treatment weighting (IPTW) to ensure a balanced analysis of covariates.

RESULTS

Of the 57,553 patients (mean age 56.0 years, 43.2% male), 16.5% used ICS and 83.5% did not. We identified 63 NTM infection cases, including nine among ICS users and 54 among non-users. Before and after IPTW, ICS use was associated with a higher risk of NTM infection (adjusted hazard ratio [HR], 4.01; 95% confidence interval [CI], 1.48 to 15.58). Higher risks were significant for patients ≥65 years (adjusted HR, 6.40; 95% CI, 1.28 to 31.94), females (adjusted HR, 10.91; 95% CI, 2.24 to 53.20), never-smokers (adjusted HR, 6.31; 95% CI, 1.49 to 26.64), systemic steroid users (adjusted HR, 50.19; 95% CI, 8.07 to 312.19), and those with higher comorbidity scores (adjusted HR, 6.64; 95% CI, 1.19 to 37.03).

CONCLUSION

ICS use in patients with chronic airway diseases might increase the risk of NTM infection, particularly in older females, never-smokers, and systemic steroid users.

Glucocorticoids in lung cancer: Navigating the balance between immunosuppression and therapeutic efficacy

Glucocorticoids (GCs), a class of hormones secreted by the adrenal glands, are released into the bloodstream to maintain homeostasis and modulate responses to various stressors. These hormones function by binding to the widely expressed GC receptor (GR), thereby regulating a wide range of pathophysiological processes, especially in metabolism and immunity. The role of GCs in the tumor immune microenvironment (TIME) of lung cancer (LC) has been a focal point of research. As immunosuppressive agents, GCs exert a crucial impact on the occurrence, progression, and treatment of LC. In the TIME of LC, GCs act as a constantly swinging pendulum, simultaneously offering tumor-suppressive properties while diminishing the efficacy of immune-based therapies. The present study reviews the role and mechanisms of GCs in the TIME of LC.

Tobacco use, self-reported professional dental cleaning habits, and lung adenocarcinoma diagnosis are associated with bronchial and lung microbiome alpha diversity

RATIONALE

The lung microbiome is an inflammatory stimulus whose role in the development of lung malignancies is incompletely understood. We hypothesized that the lung microbiome associates with multiple clinical factors, including the presence of a lung malignancy.

OBJECTIVES

To assess associations between the upper and lower airway microbiome and multiple clinical factors including lung malignancy.

METHODS

We conducted a prospective cohort study of upper and lower airway microbiome samples from 44 subjects undergoing lung lobectomy for suspected or confirmed lung cancer. Subjects provided oral (2), induced sputum, nasopharyngeal, bronchial, and lung tissue (3) samples. Pathologic diagnosis, age, tobacco use, dental care history, lung function, and inhaled corticosteroid use were associated with upper and lower airway microbiome findings.

MEASUREMENTS AND MAIN RESULTS

Older age was associated with greater Simpson diversity in the oral and nasopharyngeal sites (p = 0.022 and p = 0.019, respectively). Current tobacco use was associated with greater lung and bronchus Simpson diversity (p < 0.0001). Self-reported last profession dental cleaning more than 6 months prior (vs. 6 or fewer months prior) was associated with lower lung and bronchus Simpson diversity (p < 0.0001). Diagnosis of a lung adenocarcinoma (vs. other pathologic findings) was associated with lower bronchus and lung Simpson diversity (p = 0.024). Last professional dental cleaning, dichotomized as ≤ 6 months vs. >6 months prior, was associated with clustering among lung samples (p = 0.027, R2 = 0.016). Current tobacco use was associated with greater abundance of pulmonary pathogens Mycoplasmoides and Haemophilus in lower airway samples. Self-reported professional dental cleaning ≤ 6 months prior (vs. >6 months prior) was associated with greater bronchial Actinomyces and lung Streptococcus abundance. Lung adenocarcinoma (vs. no lung adenocarcinoma) was associated with lower Lawsonella abundance in lung samples. Inhaled corticosteroid use was associated with greater abundance of Haemophilus among oral samples and greater Staphylococcus among lung samples.

CONCLUSIONS

Current tobacco use, recent dental cleaning, and a diagnosis of adenocarcinoma are associated with lung and bronchial microbiome α-diversity, composition (β-diversity), and the abundance of several respiratory pathogens. These findings suggest that modifiable habits (tobacco use and dental care) may influence the lower airway microbiome. Larger controlled studies to investigate these potential associations are warranted.

Lower airway microbiota in COPD and healthy controls

BACKGROUND

The lower airway microbiota in patients with chronic obstructive pulmonary disease (COPD) are likely altered compared with the microbiota in healthy individuals. Information on how the microbiota is affected by smoking, use of inhaled corticosteroids (ICS) and COPD severity is still scarce.

METHODS

In the MicroCOPD Study, participant characteristics were obtained through standardised questionnaires and clinical measurements at a single centre from 2012 to 2015. Protected bronchoalveolar lavage samples from 97 patients with COPD and 97 controls were paired-end sequenced with the Illumina MiSeq System. Data were analysed in QIIME 2 and R.

RESULTS

Alpha-diversity was lower in patients with COPD than controls (Pielou evenness: COPD=0.76, control=0.80, p=0.004; Shannon entropy: COPD=3.98, control=4.34, p=0.01). Beta-diversity differed with smoking only in the COPD cohort (weighted UniFrac: permutational analysis of variance R2=0.04, p=0.03). Nine genera were differentially abundant between COPD and controls. Genera enriched in COPD belonged to the Firmicutes phylum. Pack years were linked to differential abundance of taxa in controls only (ANCOM-BC (Analysis of Compositions of Microbiomes with Bias Correction) log-fold difference/q-values: Haemophilus -0.05/0.048; Lachnoanaerobaculum -0.04/0.03). Oribacterium was absent in smoking patients with COPD compared with non-smoking patients (ANCOM-BC log-fold difference/q-values: -1.46/0.03). We found no associations between the microbiota and COPD severity or ICS.

CONCLUSION

The lower airway microbiota is equal in richness in patients with COPD to controls, but less even. Genera from the Firmicutes phylum thrive particularly in COPD airways. Smoking has different effects on diversity and taxonomic abundance in patients with COPD compared with controls. COPD severity and ICS use were not linked to the lower airway microbiota.

A Systematic Review of the Pulmonary Microbiome in Patients with Acute Exacerbation COPD Requiring ICU Admission

Background: Chronic obstructive pulmonary disease (COPD) is a major health concern. Acute exacerbations (AECOPD) may require intensive care unit (ICU) admission and mechanical ventilation. Acute infections and chronic colonization of the respiratory system are known to precipitate AECOPD. Detailed knowledge of the respiratory microbiome could lead to effective treatment and prevention of exacerbations. Objective: The aim of this review is to summarize the available evidence on the respiratory microbiome of patients with a severe AECOPD requiring mechanical ventilation and intensive care admission. Methods: A systematic literature search was conducted to identify the published papers until January 2023. The collected data were then subjected to qualitative analysis. After the first analysis, a secondary focused review of the most recent publications studying the relationship between microbiome and mortality in AECOPD was performed. Results: Out of 120 screened articles six articles were included in this review. Potentially pathogenic microorganisms (PPMs) were identified in 30% to 72% of the patients with community-acquired bacteria, gram-negative enteric bacilli, Stenotrophomonas and Pseudomonas being the most frequently isolated. During hospitalization, 21% of patients experienced colonization by PPMs. Adequate antimicrobial therapy resulted in the eradication of 77% of the identified PPMs. However, 24% of the bacteria displayed multi-drug resistance leading to prolonged or failure of eradication. Conclusion: PPMs are prevalent in a significant proportion of patients experiencing an AECOPD. The most identified PPMs include community-acquired pathogens and gram-negative enteric bacilli. Notably, no differences in mortality or duration of ventilation were observed between patients with and without isolated PPMs. However, the included studies did not investigate the virome of the patients, which may influence the microbiome and the outcome of infection. Therefore, further research is essential to comprehensively investigate the complete microbial and viral composition of the lower respiratory system in COPD patients admitted to the ICU.

Overuse of long-acting β2-agonist/inhaled corticosteroids in patients with chronic obstructive pulmonary disease: time to rethink prescribing patterns

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of morbidity and mortality globally. In the major revision of the Global Initiative for Chronic Obstructive Lung Disease (GOLD) 2023 report, the scientific committee concluded that the use of long-acting β2-agonist/inhaled corticosteroids (LABA/ICS) is not encouraged in patients with COPD. However, current prescribing patterns reveal significant use of LABA/ICS. In this paper, the evidence behind the current practice and the latest treatment recommendations is reviewed. We compare the efficacy and safety of combination therapy with long-acting muscarinic antagonist (LAMA) and LABA vs LABA/ICS and note that LAMA/LABA combinations have reduced the annual rate of moderate/severe exacerbations, delayed the time to first exacerbation, and increased post-dose FEV1 vs ICS-based regimens. The GOLD 2023 report recommends treatment with LABA and LAMA combination (preferably as a single inhaler) in patients with persistent dyspnea, with initiation of ICS in patients based on the symptoms (dyspnea and exercise intolerance as indicated by modified Medical Research Council [mMRC] score ≥ 2 and COPD Assessment Test [CAT™] > 20), blood eosinophil count (≥ 300 cells/µL), and exacerbation history (history of hospitalizations for exacerbations of COPD and ≥ 2 moderate exacerbations per year despite appropriate long-acting bronchodilator maintenance therapy). We describe practical recommendations for primary care physicians to optimize therapy for their patients and prevent overuse of ICS-based regimens. We advocate adherence to current recommendations and a greater focus on effective treatments to successfully control symptoms, minimize exacerbation risk, preserve lung function, maximize patient outcomes, and reduce the burden of drug-related adverse events.

Inhaled corticosteroids and risk of lower respiratory tract infection with Moraxella catarrhalis in patients with chronic obstructive pulmonary disease

BACKGROUND

Use of inhaled corticosteroids (ICS) is common in patients with chronic obstructive pulmonary disease (COPD) and has been associated with an increased risk of pneumonia. Moraxella catarrhalis is one of the most common bacterial causes of infectious exacerbation in COPD. Currently, to our knowledge, no studies have investigated if ICS increases the risk of lower respiratory tract infection with M. catarrhalis in patients with COPD.

OBJECTIVE

To investigate if accumulated ICS use in patients with COPD, is associated with a dose-dependent risk of infection with M. catarrhalis.

METHODS

This observational cohort study included 18 870 persons with COPD who were registered in The Danish Register of COPD. Linkage to several nationwide registries was performed.Exposure to ICS was determined by identifying all prescriptions for ICS, redeemed within 365 days prior to study entry. Main outcome was a lower respiratory tract sample positive for M. catarrhalis. For the main analysis, a Cox multivariate regression model was used.We defined clinical infection as admission to hospital and/or a redeemed prescription for a relevant antibiotic, within 7 days prior to 14 days after the sample was obtained.

RESULTS

We found an increased, dose-dependent, risk of a lower respiratory tract sample with M. catarrhalis among patients who used ICS, compared with non-users. For low and moderate doses of ICS HR was 1.65 (95% CI 1.19 to 2.30, p=0.003) and 1.82 (95% CI 1.32 to 2.51, p=0.0002), respectively. In the group of patients with highest ICS exposure, the HR of M. catarrhalis was 2.80 (95% CI 2.06 to 3.82, p<0.0001). Results remained stable in sensitivity analyses. 87% of patients fulfilled the criteria for clinical infection, and results remained unchanged in this population.

CONCLUSION

Our study shows a dose-dependent increased risk of infection with M. catarrhalis associated to ICS exposure.

Rational use of inhaled corticosteroids for the treatment of COPD

Inhaled corticosteroids (ICS) are the mainstay of treatment for asthma, but their role in chronic obstructive pulmonary disease (COPD) is debated. Recent randomised controlled trials (RCTs) conducted in patients with COPD and frequent or severe exacerbations demonstrated a significant reduction (~25%) in exacerbations with ICS in combination with dual bronchodilator therapy (triple therapy). However, the suggestion of a mortality benefit associated with ICS in these trials has since been rejected by the European Medicines Agency and US Food and Drug Administration. Observational evidence from routine clinical practice demonstrates that dual bronchodilation is associated with better clinical outcomes than triple therapy in a broad population of patients with COPD and infrequent exacerbations. This reinforces guideline recommendations that ICS-containing maintenance therapy should be reserved for patients with frequent or severe exacerbations and high blood eosinophils (~10% of the COPD population), or those with concomitant asthma. However, data from routine clinical practice indicate ICS overuse, with up to 50-80% of patients prescribed ICS. Prescription of ICS in patients not fulfilling guideline criteria puts patients at unnecessary risk of pneumonia and other long-term adverse events and also has cost implications, without any clear benefit in disease control. In this article, we review the benefits and risks of ICS use in COPD, drawing on evidence from RCTs and observational studies conducted in primary care. We also provide a practical guide to prescribing ICS, based on the latest global treatment guidelines, to help primary care providers identify patients for whom the benefits of ICS outweigh the risks.

Bronchiectasis in Europe: data on disease characteristics from the European Bronchiectasis registry (EMBARC)

BACKGROUND

Bronchiectasis is a heterogeneous, neglected disease with few multicentre studies exploring the causes, severity, microbiology, and treatment of the disease across Europe. This aim of this study was to describe the clinical characteristics of bronchiectasis and compare between different European countries.

METHODS

EMBARC is an international clinical research network for bronchiectasis. We report on a multicentre, prospective, observational, non-interventional, cohort study (the EMBARC registry) conducted across 27 European countries and Israel. Comprehensive clinical data were collected from adult patients (aged ≥18 years) at baseline and annual follow-up visits using electronic case report form. Data from individual countries were grouped into four regions (the UK, northern and western Europe, southern Europe, and central and eastern Europe according to modified EU EuroVoc classification). Follow-up data were used to explore differences in exacerbation frequency between regions using a negative binomial regression model.

FINDINGS

Between Jan 12, 2015, and April 12, 2022, 16 963 individuals were enrolled. Median age was 67 years (IQR 57-74), 10 335 (60·9%) participants were female and 6628 (39·1%) were male. The most common cause of bronchiectasis in all 16 963 participants was post-infective disease in 3600 (21·2%); 6466 individuals (38·1%) were classified as idiopathic. Individuals with bronchiectasis experienced a median of two exacerbations (IQR 1-4) per year and 4483 (26·4%) patients had a hospitalisation for exacerbation in the previous year. When examining the percentage of all isolated bacteria, marked differences in microbiology were seen between countries, with a higher frequency of Pseudomonas aeruginosa and lower Haemophilus influenzae frequency in southern Europe, compared with higher H influenzae in the UK and northern and western Europe. Compared with other regions, patients in central and eastern Europe had more severe bronchiectasis measured by the Bronchiectasis Severity Index (51·3% vs 35·1% in the overall cohort) and more exacerbations leading to hospitalisations (57·9% vs 26·4% in the overall cohort). Overall, patients in central and eastern Europe had an increased frequency of exacerbations (adjusted rate ratio [RR] 1·12, 95% CI 1·01-1·25) and a higher frequency of exacerbations leading to hospitalisations (adjusted RR 1·71, 1·44-2·02) compared with patients in other regions. Treatment of bronchiectasis was highly heterogeneous between regions.

INTERPRETATION

Bronchiectasis shows important geographical variation in causes, microbiology, severity, and outcomes across Europe.

FUNDING

European Union-European Federation of Pharmaceutical Industries and Associations Innovative Medicines Initiative.

TRANSLATIONS

For the Arabic, French, German, Greek, Hebrew, Irish, Russian and Spanish translations of the abstract see Supplementary Materials section.

LDMD: A database of microbes in human lung disease

Background

Lungs were initially thought to be sterile. However, with the development of sequencing technologies, various commensal microorganisms, especially bacteria, have been observed in the lungs of healthy humans. Several studies have also linked lung microbes to infectious lung diseases. However, few databases have focused on the metagenomics of lungs to provide microbial compositions and corresponding metadata information. Such a database would be handy for researching and treating lung diseases.

Methods

To provide researchers with a preliminary understanding of lung microbes and their research methods, the LDMD collated nearly 10,000 studies in the literature covering over 30 diseases, gathered basic information such as the sources of lung microbe samples, sequencing methods, and processing software, as well as analyzed the metagenomic sequencing characteristics of lung microbes. Besides, the LDMD also contained data collected in our laboratory.

Results

In this study, we established the Lung Disease Microorganisms Database (LDMD), a comprehensive database of microbes involved in lung disease. The LDMD offered sequence analysis capabilities, allowing users to upload their sequencing results, align them with the data collated in the database, and visually analyze the results.

Conclusion

In conclusion, the LDMD possesses various functionalities that provide a convenient and comprehensive resource to study the lung metagenome and treat lung diseases.

Effects of Fluticasone Propionate on Klebsiella pneumoniae and Gram-Negative Bacteria Associated with Chronic Airway Disease

Inhaled corticosteroids (ICS) are commonly prescribed first-line treatments for asthma and chronic obstructive pulmonary disease (COPD). Recent evidence has shown that ICS use is associated with changes in the airway microbiome, which may impact clinical outcomes such as potential increased risk for pneumonia in COPD. Although the immunomodulatory effects of corticosteroids are well appreciated, whether ICS could directly influence the behavior of respiratory tract bacteria has been unknown. In this pilot study we explored the effects of fluticasone proprionate, a commonly prescribed inhaled corticosteroid, on respiratory bacteria with an expanded focus on Klebsiella pneumoniae, a species previously implicated in fluticasone-associated pneumonia in COPD. We observed significant effects of fluticasone proprionate on growth responses of K. pneumoniae, as well as other bacterial species isolated from asthmatic patients. Fluticasone-exposed K. pneumoniae displayed altered expression of several bacterial genes and reduced the metabolic activity of bronchial epithelial cells and their expression of human β-defensin 2. Targeted assays identified a fluticasone metabolite from fluticasone-exposed K. pneumoniae cells, suggesting this species may be capable of metabolizing fluticasone proprionate. Collectively, these observations support the hypothesis that specific members of the airway microbiota possess the functional repertoire to respond to or potentially utilize corticosteroids in their microenvironment. These findings lay a foundation for novel research directions into the potential direct effects of ICS, often prescribed long term to patients, on the broader airway microbial community and on the behavior of specific microbial species implicated in asthma and COPD outcomes. IMPORTANCE Inhaled corticosteroids are widely prescribed for many respiratory diseases, including asthma and COPD. While they benefit many patients, corticosteroids can also have negative effects. Some patients do not improve with treatment and even experience adverse side effects. Recent studies have shown that inhaled corticosteroids can change the make-up of bacteria in the human respiratory tract. However, whether these medications can directly impact the behavior of such bacteria has been unknown. Here, we explored the effects of fluticasone propionate, a commonly prescribed inhaled corticosteroid, on Klebsiella pneumoniae and other airway bacteria of interest, including primary species isolated from adult asthma patients. We provide evidence of growth responses to direct fluticasone exposure in culture and further examined fluticasone's effects on K. pneumoniae, including gene expression changes and effects of fluticasone-exposed bacteria on airway cells. These findings indicate that members of the human airway bacterial community possess the functional ability to respond to corticosteroids, which may have implications for the heterogeneity of treatment response observed clinically.

A detailed analysis of possible efficacy signals of NTHi-Mcat vaccine against severe COPD exacerbations in a previously reported randomised phase 2b trial

BACKGROUND

An investigational vaccine containing non-typeable Haemophilus influenzae (NTHi) and Moraxella catarrhalis (Mcat) surface proteins did not show vaccine efficacy (VE) against combined moderate and severe (moderate/severe) exacerbations in a randomised, observer-blinded, placebo-controlled phase 2b trial of patients with chronic obstructive pulmonary disease (COPD). Nevertheless, observations on rates of severe exacerbations and hospitalisations encouraged further evaluation.

METHODS

Patients with stable COPD (moderate to very severe airflow limitation, Global Initiative for Chronic Obstructive Lung Disease [GOLD] stage 2-4), 40-80 years and at least one moderate/severe exacerbation in the last year received two doses of NTHi-Mcat vaccine or placebo plus standard care. Secondary analyses were conducted on VE against exacerbations according to severity. Potential predictive factors at baseline for VE against severe exacerbations were explored in post-hoc analyses.

RESULTS

Of 606 patients enrolled, 571 were included in the efficacy analysis (279 in NTHi-Mcat vaccine group, 292 in placebo group). VE against severe acute exacerbations of COPD (AECOPD) in various subgroups was 52.11 % (p = 0.015; frequent exacerbators), 65.43 % (p = 0.015; baseline GOLD grade 4), 38.24 % (p = 0.034; previous pneumococcal and/or influenza vaccination). VE was 52.49 % (p = 0.044) for the 6-12 months period after 1 month post-dose 2. Multivariable analysis identified two factors (frequent exacerbator status plus inhaled corticosteroid use at baseline) associated with significant VE against severe AECOPD; in this subpopulation, VE was 74.99 % (p < 0.001).

CONCLUSION

Results suggest potential efficacy with the NTHi-Mcat vaccine against severe exacerbations in certain patients with COPD, in particular those who have frequent exacerbations and use inhaled corticosteroids. This potential signal requires confirmation in an appropriately designed prospective clinical trial.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03281876.

Inhaled Corticosteroids in Adults with Non-cystic Fibrosis Bronchiectasis: From Bench to Bedside. A Narrative Review

Due to their potent anti-inflammatory capacity (particularly in predominantly eosinophilic inflammation) and immunosuppressive properties, inhaled corticosteroids (ICSs) are widely used in asthmatic patients and also in individuals with chronic obstructive pulmonary disease (COPD) who suffer multiple exacerbations or have peripheral eosinophilia. However, there is little evidence for their use in non-cystic fibrosis bronchiectasis (hereafter, bronchiectasis). According to data extracted from large databases of bronchiectasis in adults, ICSs are used in more than 50% of patients without any scientific evidence to justify their efficacy and contrary to the recommendations of international guidelines on bronchiectasis that generally advise against their use. Indeed, bronchiectasis is a disease with predominantly neutrophilic inflammation and a high likelihood of chronic bacterial bronchial infection. Furthermore, it is known that due to their immunosuppressive properties, ICSs can induce an increase in bacterial infections. This manuscript aims to review the basic properties of ICSs, how they impact bronchiectasis in adults, the current position of international guidelines on this treatment, and the current indications and future challenges related to ICS use in bronchiectasis.

Respiratory and Intestinal Microbiota in Pediatric Lung Diseases-Current Evidence of the Gut-Lung Axis

The intestinal microbiota is known to influence local immune homeostasis in the gut and to shape the developing immune system towards elimination of pathogens and tolerance towards self-antigens. Even though the lung was considered sterile for a long time, recent evidence using next-generation sequencing techniques confirmed that the lower airways possess their own local microbiota. Since then, there has been growing evidence that the local respiratory and intestinal microbiota play a role in acute and chronic pediatric lung diseases. The concept of the so-called gut–lung axis describing the mutual influence of local microbiota on distal immune mechanisms was established. The mechanisms by which the intestinal microbiota modulates the systemic immune response include the production of short-chain fatty acids (SCFA) and signaling through pattern recognition receptors (PRR) and segmented filamentous bacteria. Those factors influence the secretion of pro- and anti-inflammatory cytokines by immune cells and further modulate differentiation and recruitment of T cells to the lung. This article does not only aim at reviewing recent mechanistic evidence from animal studies regarding the gut–lung axis, but also summarizes current knowledge from observational studies and human trials investigating the role of the respiratory and intestinal microbiota and their modulation by pre-, pro-, and synbiotics in pediatric lung diseases.

Advances in inhaled corticosteroids for the treatment of chronic obstructive pulmonary disease: what is their value today?

INTRODUCTION

As of today, there is still a need to determine which COPD patients may benefit from ICS therapy, whether ICSs are useful in COPD patients without chronic bronchitis, and whether long-acting bronchodilators can reduce the risk of exacerbations in frequent exacerbators even if ICSs are not used, and whether combination therapy including ICSs is helpful in infrequent exacerbators to optimise the use of ICSs in COPD. Nevertheless, in recent years, a fair amount of evidence has been produced that, at least in part, can help define the role of ICSs in COPD better.

AREAS COVERED

Herein, the authors provide an overview of current use of ICS in COPD and discuss their value to the current treatment armamentarium. The article includes discussion of which patients will benefit best from the use of ICSs, their potential uses and adverse effects.

EXPERT OPINION

There is growing agreement on why, in whom, and when ICS therapy can be used in COPD, although the consensus is still lacking because of the heterogeneity of COPD. The use of blood eosinophil counts (BECs) is only helpful in T2 inflammation, while there is a lack of biomarkers indicating the presence of T1 and T17 immunity, which is poorly responsive to ICS. Identifying ICS-sensitive endotypes using specific biomarkers that have yet to be identified and validated is likely to demonstrate that ICSs can influence the natural course of COPD in at least a subset of patients.

Investigation on the Pathological Mechanism of Frequent Exacerbators With Chronic Obstructive Pulmonary Disease Based on the Characteristics of Respiratory Flora

Chronic obstructive pulmonary disease (COPD) is a common obstructive respiratory disease characterized by persistent respiratory symptoms and limited airflow due to airway obstruction. The present study investigates the distribution characteristics of respiratory tract flora in both frequent and infrequent exacerbators of COPD. The 16S sequencing technique was adopted to differentiate the inherent differences of respiratory tract flora between frequent exacerbators and infrequent exacerbators. Additionally, cell counting kit 8 (CCK8), lactate dehydrogenase (LDH) test, flow cytometry, enzyme-linked immunosorbent assay (ELISA), and western blot were carried out in human bronchial epithelial cells cultured in vitro and the regulatory effects of differential flora were verified. The results revealed that the observed species index, Chao1 index, and the ACE estimator of COPD frequent exacerbators were markedly higher than those of COPD infrequent exacerbators. The top five strains of COPD frequent exacerbators included g_Streptococcus (15.565%), g_Prevotella (10.683%), g_Veillonella (6.980%), g_Haemophilus (5.601%), and g_Neisseria (4.631%). Veillonella parvula generated obvious cytotoxicity and substantially reduced the activity of human bronchial epithelial cells (p < 0.01). Furthermore, the results of flow cytometry indicated that the proportion of human bronchial epithelial cells in both the S phase and G2 phase decreased following Veillonella parvula treatment indicated that Veillonella parvula inhibited cell proliferation. Meanwhile, being treated using Veillonella parvula, the expressions of interleukin-1 (IL-1), IL-6, Tumor Necrosis Factor α (TNF-α), and p-nuclear factor kappa B (NF-κB) of the cells were increased markedly (p < 0.01). Taken together, the current research demonstrated that the relative abundance of Veillonella in COPD frequent exacerbators was higher than that of infrequent exacerbators. Veillonella parvula activated the inflammatory pathway, ultimately destroyed the cell viability, and greatly impaired the activity of human bronchial epithelial cells, thereby inhibiting cell proliferation.